The invention is based on a process for coating metal workpieces with a bearing metal, wherein the workpiece is first cleaned, optionally activated, and then exposed to a galvanic chrome plating bath, to form a hard chrome plating with a hardness of at least about 600 HV (Vickers hardness scale) and having a pearl or columnar structure type, especially in accordance with German patent 25 02 284.
In this German patent a chrome plating bath is described with which glossy to metal gray chrome platings with a pearl or columnar structure type surface and having a hardness of up to about 1500 HV can be attained. These chrome platings with the trademark “Duralloy” are distinguished first by high wear resistance and second by favorable sliding or anti-friction properties, since the homogenous ball-type surface structure favors wettability and hence the formation of a stable oil film.
From European published patent application EP 0 761 844 A1 it has become known to fill in and smooth the pearl or columnar structure type surface of the hard chrome plating by galvanically applied black chromium. The black chromium is compressed in practical operation within a short time in a sort of breaking-in process, and the pearl structure is embedded. In this way, a mixed structure is obtained which, even without lubricants, has a high wear resistance with low friction values.